Fluid handling devices are well known. One type of fluid handling device is an electrically-actuated valve. Electrically-actuated valves are used in a variety of situations to control various types of fluids. Often, electrically-actuated valves are implemented where relatively fast response times are desired or where a fluid-actuated valve cannot be implemented or is not desired. In order for an electrically-actuated valve to be effective and efficient, it should consume minimal power, operate with low noise, and be cost effective to manufacture. In many applications, it is also important that the electrically-actuated valve provide an accurate and consistent fluid distribution.
One type of an electrically-actuated valve that attempts to meet the above criteria is a solenoid valve. Solenoid valves however, are typically limited in size, and in order to obtain adequate performance, a solenoid valve typically consumes a substantial amount of power. The power consumption of a solenoid valve, in some circumstances, is unacceptable. Furthermore, in some applications, it may be desirable to retain the valve in a specific open or mid-point position. If this position requires continuous actuation of the solenoid, the valve will likely consume a substantial amount of power thereby increasing the cost associated with operating the valve. In addition, solenoid valves are often expensive, large, and sometimes create an audible clicking noise as they are actuated that may be undesirable. Furthermore, the electromagnetic field generated by the solenoid valve can present problems in certain environments.
Another solution has been the use of shape memory alloys that transform shape and/or size when heated. Shape memory alloy actuated valves provide an advantage over the previously mentioned prior art solution as they can typically be manufactured smaller and generally consume less power. However, the valves have suffered in certain high temperature environments in the prior art due to a slower response time. For example, in a plunger type valve, the shape memory alloy element may be heated above its transformation temperature by passing an electrical current through the shape memory alloy element to raise the plunger against the force of a spring. In order for the plunger to return to its previous position, the shape memory alloy element must cool below its transformation temperature to allow the spring to once again seat the plunger. Because the valve cannot return to its original position until after the shape memory alloy element has cooled, shape memory alloy actuated valves have been limited in the environments they are suitable to be used. For example, until now, the valves could not be used in heated environments or be used to control heated fluids, i.e., fluids at a temperature near or above the transformation temperature. The heat from the fluid did not allow the shape memory alloy elements to cool below the transformation temperature within an acceptable time.
In an effort to overcome this problem, prior art solutions have attempted to cool the shape memory alloy elements using a cooling fluid. For example, U.S. Pat. No. 6,691,977 and U.S. Pat. No. 7,657,965 disclose shape memory alloy actuated valves that flow the fluid being controlled past the shape memory alloy elements as the fluid flows through the valve. However, both of these approaches are implemented in environments where the fluid being controlled is relatively cold, i.e., well below the shape memory alloy element's transformation temperature, to provide sufficient cooling to the shape memory alloy element. In addition, each approach provides a single inlet with a single outlet. In other words, the approaches do not allow for multiple outlets that can be coupled to various components.
Due to the above-mentioned problems, there exist certain applications that shape memory alloy actuated valves have been avoided due to the heat of the fluid being controlled. One example is in coffee machines that dispense hot water, steam, etc. In these applications, the heat of the water or steam is well above the shape memory alloy's transformation temperature. Therefore, shape memory alloy actuated valves were avoided in such situations because the temperature of the water prevented the elements from cooling below the transformation temperature at a sufficient speed.
The embodiments described below have overcome these and other problems and an advance in the art is achieved. The embodiments provide a shape memory alloy actuated valve that is cooled by the fluid being controlled. In some embodiments, the valve is cooled by the fluid prior to heating the fluid. Therefore, in this embodiment, the fluid being controlled flows by the shape memory alloy elements at a first temperature, is heated, and flows through the valve at a second temperature, which is higher than the first temperature. Therefore, the presently described embodiments cool the shape memory alloy elements even when the valve is used to control a heated fluid.